The roots of crop health: cropping practices and disease management

Much has been written and said of the importance of crop management to sustain plant health, a fundamental for feeding a world population expected to reach around nine billion by 2050. Yet, the two elements, crop management and plant health management, are generally addressed as two distinct entities, the former often being seen as a source for options for the latter. Agriculture of the Middle Age (900-1600 CE) seems not always to have distinguished crop and plant health management, considering them instead as a whole. In this article, these elements are addressed as parts of production situations, which represent a much broader level of integration for systems analysis. At the production situation level, plant disease epidemics, or their suppression, can both be seen as consequences of crop management. Modern agriculture tends to distinguish specific plant health management techniques (which are often over-emphasized) and general, non-specific ones (which are often downplayed). The former (e.g., specific host plant resistances, biological control, pesticides) may be overcome rather rapidly by plant pathogens, while the latter (e.g., crop rotation, tillage), with often progressive, incomplete, and confounded effects, may constitute the basis of sustainable management of plant health. A simulation modelling framework, with two model structures, is used to highlight the three components of disease management outlined by Berger (Annual Review of Phytopathology, 15, 165-183, 1977): (1) eliminate or reduce the initial inoculum or delay its appearance, (2) slow the rate of disease increase, and (3) shorten the time of exposure of the crop to the pathogen. The degree of involvement of these three components is further discussed in three groups of examples in plant production systems that significantly contribute to global food provisioning and food security. A few modelling outputs and evaluation of these examples suggest that, even in the most specialized production situations, both specific and non-specific plant health management strategies are necessary for sustained health of our crops and for durable performances of agricultural systems.